fanning fiberglass in attic - dumb idea?

The paper masks do nothing more than make you feel better, IMO. Unless a mask fits tight against the face you'll just be pulling air in from around the edges. Get a rubber mask, either with cartridges, or a paper element in the middle. The type of filtration depends on what your hazard is. But the important thing is that the mask makes an airtight fit on your face.